Numerous machines already exist for performing the aforenoted packing operation.
Examples thereof can be found in documents U.S. Pat. No. 4,894,975 and U.S. Pat. No. 4,709,533.
As shown in accompanying FIG. 1, automatic machines are known for forming, filling, and closing packaging bags formed from films of thermoplastic material and fitted with add-on strips and comprising:
a tube-forming neck 10 which is fed with film 1 in a planar state from a suitable pay-out means, and which outputs the film shaped into a tube 2; PA1 a filling chute 20 which opens out into the forming neck 10 and consequently into the tube 2; PA1 means 50 for feeding strips 3; PA1 means 30 for performing longitudinal heat sealing 31 so as to fix the strips 3 on the longitudinal margins of the film 1 and to seal these longitudinal margins of the films together in order to close the tube 2 longitudinally; and PA1 means 40 suitable for sequentially generating a first transverse line of heat sealing 42 before a product is inserted into the tube 2 by means of the filling chute 20, and then a second transverse line of sealing 44 once the product has been inserted into the tube 2, thereby closing the package around the product. PA1 flexible film feed means; PA1 strip feed means; and PA1 fixing means for fixing the strips onto the flexible film by heat sealing; PA1 the strip feed means are adapted to deliver a tape of flexible material carrying the complementary strips; and PA1 the fixing means are adapted to heat seal the tape onto the film prior to the resulting assembly being fed to a tube-forming neck. PA1 means suitable for heat sealing one wing of the tape provided with the closure strips onto a first length of the film; PA1 means suitable for folding the film; and PA1 means suitable for heat sealing the second wing of the tape onto the second length of the film so as to form a Z-shape at the closure prior to feeding the assembly comprising the film and the tape to the forming neck.
State of the art machines of the kind shown in accompanying FIG. 1 have already exhibited good service.
Nevertheless, they are not completely satisfactory.
In particular, installing the closure strips often turns out to be very difficult and requires regular attention, thereby slowing down the manufacturing process. Also, such installation requires major modifications whenever it is desired to transform conventional automatic machines for forming, filling, and closing packaging bags formed from films of thermoplastic materials.